I'm just over here making soil science memes, and you got to get all serious on me.

Sandy clay does exist, but it is very rare. Look at the size of the box on the triangle. Typically, it's only found in specific settings where you've had waterlain sediment with periodic flooding. The water has to move very quickly (to deposit only sand) and then have a period of stagnation to allow for the clay particles to settle out.

Because this is a rare occurrence in nature, the joke is that it doesn't exist